Casting a spell requires a hero to have 1 hand free (or a held spellcasting focus), the ability to speak, and may require mana as well. A spell’s mana cost is equal to its spell tier; cantrips cost no mana (see “Spells” on page 45 for more).
Upcasting Spells. Some spells have a greater effect for each additional mana spent on them. A hero can upcast a spell only up to the tier they have unlocked.